Paying £300,000 instead of £3,000, and other mix-ups

A recent Magazine article about great miscalculations - inspired by the French railway company's purchase of trains that are too wide for many platforms - prompted readers to share their own mistakes.

The piece listed 10 examples where a little error has had large repercussions. Your stories were rarely on such an epic scale - but equally embarrassing.

John R, Woking: While working as an accounts assistant for a large sportswear company in the UK, I paid a foreign supplier £300,000 ($500,000) instead of £3,000 ($5,000) for some samples. I realised my mistake on my last day working there but did 'fess up to the boss before I left the building. He already knew.

Nigel Parsons, Sheffield: In the summer of 1973 I spent many days chipping concrete off the ends of a new half-Olympic 25m swimming pool in Chester-le-Street because the surveyor laying it out had forgotten to allow for the thickness of the tiles. Not urban myth, I was there!

Paul Belmonte, Edinburgh: While working as a hotel night porter, I miscalculated the adjustment of the automatic wake up system for British Summer Time, meaning some guests arrived for breakfast at four in the morning, instead of the 06:00 start they'd asked for!

Graham Sheedy, Hest Bank, Lancashire: A colleague of mine once ordered a metal cylinder that was to be used to extend a boiler chimney on the petrochemicals site where we worked. The diameter was 792mm but he ordered one with a 792-inch diameter. His suspicions were aroused when the procurement department told him they were having trouble getting the item but were pleased to have found a Japanese submarine manufacturer who could make it! He checked his dimensions after this and revised his order.

Derek Roberts, Ferring, West Sussex: I once had the task of installing a cat flap into a door between my garage and my house. I carefully measured and marked the hole required, and took the door off its hinges to cut the hole - but once the door was on the bench, I couldn't find the markings. I assumed they were on the reverse of the door, so I marked it up again and cut the hole. I brought the door back to the frame but the hinges were in the wrong place... then I noticed the scuff marks were at the top of the door... I'd put the cat flap in at the wrong end. Many helpful comments about trampolines and ladders were to follow!

Paul Jinks, Reading, Berkshire: Many years ago our company issued a directive that the metric system was now to be used for everything. Drawings and production were to be in millimetres. I ordered a small plastic sign about the size of a credit card to be placed on some electronic equipment not to be moved, because it transmitted interference. After some weeks had passed I got concerned... So I rang our sign-making department to inquire about the delay. They said they there were having trouble finding a truck to deliver it. Very mysterious... until it eventually arrived. They had assumed millimetres were feet! It was about 80ft by 50ft (24m by 15m) and would not fit through the door.

Bill Gardner, Nottingham: The first time I ordered groceries online I mixed up quantities with weight. My kids had a good laugh at me when I opened a bag to find one carrot and one apple instead of a kilo of each.

Lawrence Braden, Concord, New Hampshire, US: On 6 May, 1954 all the news was about Roger Bannister breaking the four-minute mile. I, a curious 11-year-old, of course wanted to find out how long it would take me to run the same distance. I knew our track at school was 100 yards in length, and found out that there were 5,280 feet in a mile, and calculated how many times I would have to run around the track to run a mile. I spent most of my lunch hour running... three miles! I had confused yards and feet! Instead of making 17.6 circuits, I had run around the thing 52.8 times, all of this in the desert heat of Bakersfield, California. Not that dramatic, for sure, but this made me very very careful about units years later in physics classes at Berkeley.

Bill Nettles, Jackson, Tennessee, US: I was building rafters for a building in a village in Romania. After measuring the width of the building, we built a pattern, cut the lumber and fashioned the rafters. As we began setting them in place, they were a foot too narrow. I re-measured the width, and a co-worker re-measured the rafter. They were the same, until someone noticed that the tape I was using (which I had borrowed), had a one-foot "high precision" section at the beginning of the tape, then the measurements restarted (from a false zero point) so that all measurements from the physical end of the tape were reading one foot shorter than reality. We were able to use the rafters by nailing extensions to them, but the pitch was a bit odd. The co-worker later snipped off the end of that tape measure.

Alasdair, Glasgow: I was asked by an elderly aunt a few years ago to measure blinds for her windows. I was visiting a few weeks later and commented on how well the blinds looked. She agreed but rather sharply said that they had to pay twice for the biggest one as it had been mis-measured. Surprised, I got the tape from the cupboard and checked again. She told me I shouldn't have used that tape as it had fallen in the fire and her husband had rejoined it between the 34-inch and 40-inch segments.

John Richards, Cardiff: Not sure I should publicly confess to this one, but it is many years ago now... In 1982, I got married and we bought a small, cheap, house as many newlyweds do, with a bit of work needing to be done on it. Money was tight and everything had to be done with as little waste as possible, so my dubious skills as a quantity surveyor were in demand. We decided, mostly for reasons of economy but to be fair it was fashionable in those days, to do the living and dining rooms in woodchip and paint it.

I sat myself down with pen and paper and a cup of tea for some planning. The size of the rooms required 27 drops of woodchip, and I double checked this calculation so as to be sure of the amount required. Come Saturday morning, off I confidently went to the local hardware shop, which was having an offer on woodchip, reduced from 90p ($1.50) a roll to 60p ($1). This may have had some bearing on the mistake I was about to make. Into the shop I boldly and confidently strode.

I asked for 27 rolls (yes, rolls, not drops) of woodchip! Just as well they were on offer, really. Even when I was staggering up the road trying to balance this ridiculous load, I was still absolutely confident I'd bought the right amount. I even reckoned that, if I was careful with the cutting, there would be enough to do the under-stairs cupboard. In the event, we did the entire house, two of my mates' houses as well, and my father still had a few rolls in his garage when he died 10 years ago!